The present invention relates to a spray nozzle for electrostatic airless coating.
In a conventional spray gun for electrostatic airless coating, a flat spray nozzle is utilized for making a spindleshaped spray pattern. In this construction, however, as the discharge pressure is increased, the spraying speed of coating material is raised and the particles of the coating material tend to be out of the electric field. Consequently, the adhesion efficiency of the coating material is lowered.
On the other hand, when the discharge pressure is decreased, tails are produced on the longitudinal ends of the pattern to make the distribution of the coating material uneven and provide a rough coating surface with too coarse particles of the coating material deposited thereon. This is because the spray is sectorshaped and an electrode member, such as a corona pin, producing the electric field and charging the particles of the coating material is provided only at a single point in the vicinity of the ejection port. Namely, the flat spray nozzle necessarily produces tails as aforementioned, and since the electrode member is provided only at a single point in the vicinity of the ejection port, the electric field is deflected from the axis of the ejection port to produce an uneven distribution of the coating material.